Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.1): between the years 1826 and 1836 : describing their examination of the southern shores of South America, and the Beagles's circumnavigation of the globe

60 GABKIEL CHANNEL. Feb. 1827. The rock, of course, decomposes equally on both sides ; but on that exposed to the south wind, it breaks off in flakes parallel to the direction of the strata, and therefore does not make the course of the beach more irregular; while on the other side it moulders away transversely to the direction of the dij), leaving holes, in which water lodges, and hastens decomposition by entering deeply into the interstices. Water, air, and frost decompose the rock, and form a soil, which, if not too much exposed to the wind, is soon occupied by vegetation. The rugged faces of the cliffs, on the southern shore, caused by the rock decomposing across the grain, collect sand and mud ; and hence it happens that anchorages are frequently found on one side, whilst, on the other, the anchor will not hold, from the steepness of the ground ; there being nothing upon the smooth declivity to retain mud and sand before it gets to the bottom ; which, in most cases known to me, lies far beyond the reach of the anchor. After a tedious and difficult passage through the Gabriel Channel, we anchored in a snug harbour within the entrance of Magdalen Channel, on the west side, under a peaked hill called by Sarmiento ' El Vernal,' — in our plan, the ' Sugar- loaf.' The entrance is about a quarter of a mile wide ; but after a few hundred yards the harbour opens, extending in for nearly a mile. It is of easy depth ; seven fathoms in the entrance, and four, five, and six fathoms within ; so that it is